The hiking book:None. We just wandered on some trails.The distance: 4-ish milesThe CityGirls rating: 7

AM recently returned to our city by the bay from three months in the flatlands of the Midwest. So, for her first hike back, we decided to re-introduce her to the ocean with a wander through the Marin Headlands.

There were no stunning ocean vistas this time, though. Instead, an ocean of fog.

And hills. Oh yeah. AM had forgotten what real hills were like. We slogged up the hills above Rodeo Beach until we were just above the fog, legs burning and hearts pounding with exertion.

Up in these hills are the remains of all sorts of fortifications from when there were active forts and armaments here protecting San Francisco Bay and the city. We’ve hiked by Battery Townsley and looked out at the vista that was covered by its 16-inch gun during and after World War II. We’ve seen the Nike Missile Site and stood at the top of Hill 88 where radar watched for incoming enemy planes and stood ready to direct the Nike missiles.

On this hike we passed more of the fortifications of Battery Townsley, including some lookout posts with very peculiar construction. These were simple, shallow roosts where soldiers had kept watch or manned anti-aircraft guns, but they were formed out of what looked like sandbags that had petrified into rock.

We puzzled over how these sandbag rocks had come to be. Were they sandbags filled with concrete that hardened into rock as they dried? Or were they true sandbags that have solidified into rock from years of exposure to the sea, wind, and rain?

Despite the fog, AM found a nice rock on which to sun herself, and even a very little bit of sunlight to sun in.

We hiked up the Coastal Trail, with a few detours along the many unmarked trails that branch off of it. From the top of the first ridge above Rodeo Beach, we took the Wolf Ridge trail down towards Tennessee Valley, then the Miwok Trail back to Rodeo Lagoon and the beach.

We passed a whole slew of birds frolicking in the lagoon, including a pair of herons and some fun dark birds balancing on posts sticking up out of the water. A couple of the birds on smaller posts kept unfurling their wings, perhaps to keep their balance.

Back at Rodeo Beach, the fog had finally burned off enough to be able to see the ocean, and AM said hello, and good to see you again.

Just as we were pulling out of the parking lot to head home, we saw a sea lion jump in the waves just beyond the surfers at Rodeo Beach! And a moment later, a dolphin fin followed after it! The carousing sea creatures put smiles on our faces as we drove through the fog bank back home.